Stem cells refer to cells capable of differentiating into at least two types of cells while having self-replicating ability and may be classified into totipotent stem cells, pluripotent stem cells, and multipotent stem cell. Totipotent stem cells are cells having totipotent properties capable of developing into one perfect individual, and these properties are possessed by cells up to eight-cell stage after the fertilization of an oocyte and a sperm. When these cells are isolated and transplanted into the uterus, these cells may develop into one perfect individual. Pluripotent stem cells, which are cells capable of developing into various cells and tissue derived from the ectodermal, mesodermal and endodermal layers, are derived from an inner cell mass located inside of blastocysts generated after 4-5 days of fertilization. These cells are called “embryonic stem cells” and may differentiate into various other tissue cells but do not form new living organisms. Multipotent stem cells, which are stem cells capable of differentiating into only cells specific to tissue and organs containing these cells, are involved not only in the growth and development of various tissue and organs in the fetal, neonatal and adult periods but also in the maintenance of homeostasis of adult tissue and the function of inducing regeneration upon tissue damage. Tissue-specific multipotent cells are collectively called “adult stem cells”.
The adult stem cells, which are obtained by harvesting cells already existing in various organs of human body to develop the cells into stem cells, are characterized by differentiating into only specific tissue. However, recently, experiments for differentiating adult stem cells into various tissue including liver cells, and the like, are successful, which is in the spotlight. Particularly, in regenerative therapy, which is therapy performed by actively utilizing cells for regeneration of biological tissue and organ having functional disorder or dissonance caused by a disease or accident and recovery of functions, a method including: collecting stem cells, blood-derived mononuclear cells, or bone marrow-derived mononuclear cells, inducing cell proliferation and/or differentiation by in vitro culture, and transducing selected undifferentiated (stem cells and/or precursor cells) and/or differentiated cells in a patient's body by implantation has been mainly used. As it is estimated that the existing method for treating a disease through classic medicine treatment methods or surgical methods will be replaced by cell/tissue replacement therapy for replacing damaged cells, tissue, or organs with healthful cells, tissue, or organs as described above, usages of the stem cells will be further increased.
Therefore, currently, various functions of the stem cells have been studied. Among them, cell therapy using mesenchymal stem cells has been spotlighted, and a technology of improving mesenchymal stem cells isolated from a human body so as to be suitable for treatment has been developed (WO 2006/019357, Korean Patent No. 0795708, and Korean Patent No. 0818214).
However, research into a method of preparing stem cells suitable for intracorporeal administration and having excellent safety has not been sufficiently conducted yet.
Therefore, the present inventors confirmed that in the case of suspending stem cells in a solution containing aspirin, disruption and aggregation of stem cells may be prevented, thereby completing the present invention.